Method for controlling invertebrate pests and/or fungal diseases which affect potatoes or other crops

ABSTRACT

A method of protecting crop plants by controlling phytophagous invertebrate pests and/or plant diseases caused by fungal pest is disclosed. The method involves applying a series of doses of an aqueous mixture containing an effective amount of a crop protection agent to the locus of the roots of the crop plants by means of perforated or porous conduit (e.g., tubing or irrigation tape) on or near the surface of the soil. At least one dose of the series is applied in the period from one week prior to planting to two days prior to harvest; and at least two doses of the series are applied at least two days apart during the growing season of the crop or the infestation period of a pest being controlled.

BACKGROUND OF THE INVENTION

The control of invertebrate pests is extremely important in achievinghigh crop efficiency. Damage by invertebrate pests to growing and storedagronomic crops can cause significant reduction in productivity andthereby result in increased costs to the consumer.

The potato crop is an important crop in Europe and other parts of theworld but production is frequently affected by a significant number ofarthropod and nematode pests. Current estimates for the United Kingdom(UK) alone indicate that nematodes cost growers ±50 million in controlstrategies and lost production on an annual basis (MAFF (1999) PotatoCyst Nematode: A Management Guide, Editor W. Parker, MAFF Publications,pp. 1-33. Hereafter: MAFF, 1999). The nematode pests have also beenreported in other potato growing regions of the world from North andSouth America to mainland Europe and South Africa (Turner, S. J. andEvans, K. 1998, The origins, global distribution and biology of potatocyst nematodes (Globodera rostochiensis (Woll.) and Globodera pallidaStone), in Potato Cyst Nematodes. Biology Distribution and Control. EdsMarks, R. J. and Brodie, B. B. CAB International, pp. 749). Key nematodepests are Globodera pallida, Globodera rostochiensis, Trichodorusspecies, Paratrichodorus species and Longidorus species.

G. pallida and G. rostochiensis are commonly known as cyst nematodes. Itis thought that the pest was introduced from the Andean region of SouthAmerica into the United Kingdom and subsequent trade of infected tubers(or soil on tubers) resulted in the spread to other regions.

When potatoes are planted the emerging roots produce an exudate thatstimulates the eggs from a previous infestation to hatch. The hatchednematodes (all male) are attracted to the root and subsequently feed(causing damage) and invade the root tissues. The feeding process insusceptible varieties of potato causes some of the male nematodes tobecome female. Mating occurs as the body of the female erupts throughthe wall of the root. The cysts that are visible on the root are theswollen female body that can contain up to 600 eggs. The leathery cystsfall from the roots and are the mechanism of survival of the pest fromcrop to crop. Thus the multiplication of the pest can be up to 50-foldfrom the original infestation. The egg viability declines at 15-30% perannum (depending on species) and growers should use wide rotations toassist in the control process (ideally 1 year in 7) but economicpressures often result in crops being grown 1 year in 3. This practicecompounds the problem, allowing infestation to be sustained.

The damage to potatoes is not only evident in terms of significant yieldloss but also in terms of effects on produce quality. The nematode pestsare particularly pernicious and enduring as the pest may be multipliedsignificantly on a crop and the residual effects may continue for up to30 years in the form of eggs which remain viable from crop to crop.

Whilst the development of resistant and tolerant varieties of potatoes,use of rotations and intervention with chemicals has assisted in themaintenance of production, the problem of nematodes that affect potatoesis increasing in countries where potatoes are being grown intensively.

Current chemical control methods rely on the use of soil fumigation thatis conducted before the crop is planted and/or granular nematocides thatare applied at planting. The fumigant nematocides are used to sterilisethe soil when pest burdens are high. However, the fumigants aretypically toxic to plants which necessitates their use before the cropis planted. Moreover, soil fumigants are not completely effective, sincetheir efficacy depends upon how effectively the soil can be sealed inorder to retain the fumigant. Subsurface application of liquid fumigantsfor controlling nematodes has been reported (T. J. W. Alphey, Hort. Res.1981, 21, 169-180). Typically the degree of control is rarely in excessof 80% (MAFF, 1999). The significance of this is that the 20% of peststhat survive can still cause damage to potatoes and multiply again onthe crop. In order to control the residual population, it is usuallynecessary to apply a granular nematicide after fumigation, at planting.The two treatments add significant cost to the production of potatoes.Where infestations are low to moderate the use of granular nematocidesby soil incorporation at planting is the conventional practice. Granularnematocides, provided they are incorporated correctly, can provide up to95% control (depending on the species present).

As noted above, a combination of rotation and nematicide use has beensuccessful in keeping infestation at a low level. However, thedevelopment of varieties of potato resistant to G. rostochiensis hasallowed the selection of G. pallida (for which there is no or poorresistance in current potato varieties) which hatches from the eggs inthe soil over a longer period. It is generally accepted that thehatching period for G. rostochiensis is typically 4-6 weeks and thehatching period for G. pallida is typically 6-8 weeks. In addition, thepersistence of the nematicide to cover the entire hatching period,whilst generally adequate for G. rostochiensis, is often insufficient tocover the entire hatching period of G. pallida (Whitehead, A. G., Tite,D. J., Fraser, J. E. and Nichols, A. J. F., Differential control ofpotato cyst nematodes, G. rostochiensis and G. pallida by oxamyl and theyields of resistant and susceptible potatoes in treated and untreatedsoils, Annals of Applied Biology, 1984, 105, pp 231-244. Hereafter:Whitehead et al 1984). Thus the nematicide has decreased in the soil tolevels where effective control is not always possible, resulting in somedamage to the potatoes and multiplication of the pest. Surveys conductedin the United Kingdom illustrate that G. pallida is now the dominantspecies (44% incidence in 1993 and 74% incidence in 1997, MAFF, 1999).

In certain soils (Sands) in the United Kingdom the presence offree-living nematodes from the Trichodorus genera also damage potatoesby direct feeding on roots. However, the main economic damage from thesenematodes is caused by the transmission of tobacco rattle virus (TRV)which causes necrotic arcs in tubers rendering them unsaleable (French,N. and Wilson, W. R., Influence of Crop Rotation, Weed control andNematocides on Spraing in Potatoes, Plant Pathology, 1976, 25,pp167-172). There are also other free-living species in some countries(Meloidgne spp.) which also feed on roots causing significant damage(Harris, P., The Potato Crop. The Scientific Basisfor Improvement.Chapman and Hall, 1978).

Granular nematocides were first developed in the middle of the 1970swhen the predominant species was G. rostochiensis. The shift to thepredominance of G. pallida requires a re-evaluation of controlstrategies for this important pest of potatoes.

Other arthropod pests (larvae of the Coleoptera and Lepidoptera familiesand aphids from the Homoptera family which are also virus vectors) alsocontribute to significant losses in potatoes in many regions of theworld. The inherent solubility and dispersion of nematocides in soilalso provides control of certain other soil-dwelling arthropods such aswire worm, Agriotes spp. (a coleopteran larval stage which burrows intothe tuber). Nematocides, because of their systemic nature also cancontrol pests such as aphids and other arthropod pests that infest thearial parts of the plants. Other pests of potato for which control isdesired include Phthorimaea operculella (potato tuber moth),Leptinotarsa decemlineata (Colorado Beetle), Empoasca fabae (greenleafhopper) and Eupterycyba jucunda (potato leafhopper).

Oxamyl, also known asN,N-dimethyl-2-methylcarbamoyloxyimino-2-(methylthio)acetamide (see U.S.Pat. No. 3,530,220 and U.S. Pat. No. 3,658,870), was introduced in theUnited Kingdom in the middle of the 1970's for the control of many ofthe pests described above in potatoes. The product has been veryeffective in controlling G. rostochiensis but, for the reasons indicatedabove, the efficacy could be improved given the shift towards thedominance of G. pallida. Oxamyl is also effective in controlling chewingand sucking insects (including soil insects) and spider mites. Othercarbamate nematocides and organophosphorous nematocides may be used forthe same purpose and in a similar manner. Thus, improved methods ofcontrol using oxamyl and/or the other nematocides are needed.

The control of plant diseases caused by fungal plant pathogens is alsoextremely important in achieving high crop efficiency. Plant diseasedamage to ornamental, vegetable, field, cereal, and fruit crops cancause significant reduction in productivity and thereby result inincreased costs to the consumer. Many treatments are commerciallyavailable for these purposes, but the need continues for new methods forcontrolling disease that are more effective, less costly, less toxic, orenvironmentally safer.

As noted above, the potato is an important crop in the United Kingdomand many other regions of the world. Fungal pathogens of the potatoinclude Phytophthora infestans (the causal agent of potato and tomatolate blight) and Altemaria solani (the causal agent of potato earlyblight). Damage to potato crops from these fungal diseases can besevere, leading to complete defoliation of infected plants.

Suppression of lettuce drop caused by the fungal plant pathogenSclerotinia minor by subsurface drip irrigation versus furrow irrigationhas been attributed to differential moisture and temperature effects (A.A. Bell, L. Liu, B. Reidy, R. M. Davis and K. V. Subbarao,Phytopathology, 1998,88,252-259.

It is known that certain pesticides can be applied to plants usingirrigation techniques (e.g., drip irrigation) (see e.g., U.S. Pat. No.5,696,094, U.S. Pat. No. 5,698,592, U.S. Pat. No. 5,830,919 and U.S.Pat. No. 6,107,314).

SUMMARY OF THE INVENTION

This invention relates to a method of protecting crop plants bycontrolling phytophagous invertebrate pests and/or plant diseases causedby fungal pests (i.e. fungal pathogens). The method comprises applying aseries of doses of an aqueous mixture containing an effective amount ofa crop protection agent to the locus of the roots of the crop plants bymeans of perforated or porous conduit (e.g., tubing or irrigation tape)on or near the surface of the soil; at least one dose of said seriesbeing applied in the period from one week prior to planting to two daysprior to harvest; and at least two doses of said series being applied atleast two days apart during the growing season of the crop or theinfestation period of a pest being controlled. Using the methodsoil-inhabiting invertebrate pests or fungal diseases caused bysoil-inhabiting fungal pathogens may be controlled by applying aneffective amount of the aqueous mixture to the soil. In addition,foliar-inhabiting invertebrate pests or fungal diseases caused byfoliar-inhabiting fungal pathogens may be controlled by applying aneffective amount of the aqueous mixture containing a crop protectionagent which is then taken up by the plant from the soil.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 qualitatively represents a decline curve of oxamyl in the soilafter a single application plotted together with infestation curves fortwo nematode species in untreated soil in the United Kingdom.

FIG. 2 qualitatively represents a series of decline curves of oxamyl inthe soil after a series of four applications plotted together with thetwo infestation curves included in FIG. 1.

FIG. 3 represents a typical field layout of a trickle irrigation systemthat may be used to apply a crop protection agent in accordance withthis invention.

FIG. 4 represents a closed system injection apparatus that may be usedfor mixing a liquid concentrate of crop protection agent with waterprior to application of the agent.

FIG. 5 represents a Venturi apparatus for mixing a liquid concentrate ofcrop protection agent with water prior to application of the agent.

FIG. 6 relates to Test A and represents the number of G. pallida cystsper gram of root mass for several treatment protocols in soil amendedwith 24 cysts/pot (estimated to be 10 eggs/g of soil) prior totreatment.

FIG. 7 relates to Test A and represents the number of G. pallida cystsper gram of root mass for several treatment protocols in soil amendedwith 120 cysts/pot (estimated to be 50 eggs/g of soil) prior totreatment.

DETAILS OF THE INVENTION

The present invention has been designed to effectively apply existingcrop protection agents (e.g. oxamyl) or new crop protection agents usingaqueous formulations and a liquid delivery system (e.g., a drip ortrickle irrigation system), thereby improving the control of perniciouspests affecting crops (e.g., potatoes). The novel control strategy isbased upon two elements:

-   -   Serial applications of an aqueous mixture containing an        appropriate crop protection agent; and    -   The use of an application system that applies the aqueous        mixture on or below the soil surface.

The temporal distribution of the doses of the crop protection agent(e.g., oxamyl) to the locus of the roots (e.g. the roots of a potatocrop) may be controlled in accordance with this invention to providediscrete aliquots of the crop protection agent which match theinfestation dynamics of the pest.

The application system may be for example, an irrigation system used bygrowers to supply water to optimize crop growth and development (e.g.the trickle tape system described below). A suitable apparatus forapplying a crop protection agent to the locus of the roots of cropplants in a crop field in accordance with this invention might comprise,for example:

-   (a) a mixing means of incorporating the crop protection agent into a    water supply to provide an aqueous mixture;-   (b) a pump for pumping the aqueous mixture from the mixing means;-   (c) one or more supply pipes running from the mixing means to the    crop field;-   (d) a plurality of perforated or porous conduits, running from said    supply pipes, on the soil surface or beneath the soil surface in the    loci of the roots of the crop plants;-   (e) a means for regulating the concentration of crop protection    agent in the aqueous mixture and the frequency of application of the    crop protection agent.

The method of this invention might thus comprise (i) incorporating thecrop protection agent into a water supply to provide an aqueous mixturecontaining said crop protection agent; (ii) pumping the aqueous mixturethrough one or more supply pipes to distribute the crop protection agentto a plurality of perforated or porous tubing or irrigation tape on thesoil surface or beneath the soil surface in the loci of the roots of thecrop plants throughout the crop field; and (iii) regulating theconcentration of crop protection agent in the water supply and thefrequency of application of the crop protection agent to providecontinual crop protection.

The term “aqueous mixture” means a mixture of the crop protection agentin mixture with water (e.g. irrigation water) at a concentrationcommensurate with the delivery (on a per hectare basis) of effectiveamounts of the active ingredient. The aqueous mixture may furthercomprise an agriculturally suitable carrier comprising at least one of aliquid diluent or a surfactant. The phrase “on or near the soil surface”means at the soil surface or within a region extending from a locationabove the soil surface where the aqueous mixture can be discharged fromthe conduit and effectively applied to the soil surface to a locationbelow the soil surface where the aqueous mixture can be discharged fromthe conduit and effectively applied to the plant root zone. This regioncan vary from crop to crop and according to the growth stage of aparticular crop, but generally includes the region extending on averagefrom about 30 cm above the soil surface to about 30 cm below the soilsurface. Of note are embodiments where the conduit is located within theregion extending on average from the soil surface to 30 cm below thesoil surface. Of particular note for potatoes are embodiments wheretrickle tape is located on average between the soil surface and the topof the planted tuber. The term “growing season” means the period of timefrom planting of the crop plant (e.g. from seed, tuber, or transplant)until harvest. This period, depending on the crop, may have a durationas long as approximately forty weeks. The term “pest infestation period”means the period of time during a single growing season of the crop whena particular pest propagates or multiplies and infests the cropplant(s). Infestation typically results in damage or yield loss. Forexample, the infestation period for cyst nematodes lasts from time ofplanting of the potato to ten weeks after planting.

Added elements may also be incorporated into the control strategy. Forexample, a closed transfer system may be used for mixing the liquidcomposition (e.g. a composition comprising oxamyl and/or other activeingredients) with water for delivery to the crop for the control of thestated pests or diseases.

Description of Invertebrate Pests and Foliar Diseases

As referred to in this disclosure, the term “phytophagous invertebratepest” refers to invertebrate pests causing injury to plants by feedingupon them, such as by eating foliage, stem, leaf, fruit or seed tissueor by sucling the vascular juices of plants. Phytophagous invertebratepests include various arthropods, gastropods and nematodes of economicimportance as pests to plants. The term “arthropod” includes insects,mites, centipedes, millipedes, pill bugs and symphylans. The term“gastropod” includes snails, slugs and other Stylommatophora. The term“nematode” includes the phytophagous nematodes (Phylum or ClassNematoda). Economically important phytophagous invertebrate pestsinclude: larvae of the order Lepidoptera, such as armyworms, cutworms,loopers, and heliothines in the family Noctuidae (e.g., fall armyworm(Spodoptera fugiperda J. E. Smith), beet armyworm (Spodoptera exiguaHübner), black cutworm (Agrotis ipsilon Hufnagel), cabbage looper(Trichoplusia ni Hübner), tobacco budworm (Heliothis virescensFabricius)); borers, casebearers, webworms, coneworms, cabbageworms andskeletonizers from the family Pyralidae (e.g., European corn borer(Ostrinia nubilalis Hubner), navel orangeworm (Amyelois transitellaWalker), corn root webworm (Crambus caliginosellus Clemens), sod webworm(Herpetogramma licarsisalis Walker)); leafrollers, budworms, seed worms,and fruit worms in the family Tortricidae (e.g., codling moth (Cydiapomonella L. (L. means Linnaeus)), grape berry moth (Endopiza viteanaClemens), oriental fruit moth (Grapholita molesta Busck)); and manyother economically important lepidoptera (e.g., diamondback moth(Plutella xylostella L.), pink bollworm (Pectinophora gossypiellaSaunders), gypsy moth (Lymantria dispar L.)); foliar feeding larvae andadults of the order Coleoptera including weevils from the familiesAnthribidae, Bruchidae, and Curculionidae (e.g., boll weevil (Anthonomusgrandis Boheman), rice water weevil (Lissorhoptrus oryzophilus Kuschel),rice weevil (Sitophilus oryzae L.)); flea beetles, cucumber beetles,rootworms, leaf beetles, potato beetles, and leafminers in the familyChrysomelidae (e.g., Colorado potato beetle (Leptinotarsa decemlineataSay), western corn rootworm (Diabrotica virgifera virgifera LeConte));chafers and other beetles from the family Scaribaeidae (e.g., Japanesebeetle (Popillia japonica Newman) and European chafer (Rhizotrogusmajalis Razoumowsky)); wireworms from the family Elateridae and barkbeetles from the family Scolytidae; adults and larvae of the orderDermaptera including earwigs from the family Forficulidae (e.g.,European earwig (Forficula auricularia L.), black earwig (Chelisochesmorio Fabricius)); adults and nymphs of the orders Hemiptera andHomoptera such as, plant bugs from the family Miridae, cicadas from thefamily Cicadidae, leafhoppers (e.g. Empoasca spp.) from the familyCicadellidae, planthoppers from the families Fulgoroidae andDelphacidae, treehoppers from the family Membracidae, psyllids from thefamily Psyllidae, whiteflies from the family Aleyrodidae, aphids fromthe family Aphididae, phylloxera from the family Phylloxeridae,mealybugs from the family Pseudococcidae, scales from the familiesCoccidae, Diaspididae and Margarodidae, lace bugs from the familyTingidae, stink bugs from the family Pentatomidae, cinch bugs (e.g.,Blissus spp.) and other seed bugs from the family Lygaeidae, spittlebugsfrom the family Cercopidae squash bugs from the family Coreidae, and redbugs and cotton stainers from the family Pyrrhocoridae; adults andlarvae of the order Acari (mites) such as spider mites and red mites inthe family Tetranychidae (e.g., European red mite (Panonychus ulmiKoch), two spotted spider mite (Tetranychus urticae Koch), McDaniel mite(Tetranychus mcdanieli McGregor)), flat mites in the familyTenuipalpidae (e.g., citrus flat mite (Brevipalpus lewisi McGregor)),rust and bud mites in the family Eriophyidae and other foliar feedingmites; adults and immatures of the order Orthoptera includinggrasshoppers, locusts and crickets (e.g., migratory grasshoppers (e.g.,Melanoplus sanguinipes Fabricius, M. differentialis Thomas), Americangrasshoppers (e.g., Schistocerca americana Drury), desert locust(Schistocerca gregaria Forskal), migratory locust (Locusta migratoriaL.), mole crickets (Gryllotalpa spp.)); adults and immatures of theorder Diptera including leafininers, midges, fruit flies (Tephritidae),frit flies (e.g., Oscinella frit L.), soil maggots and other Nematocera;adults and immatures of the order Thysanoptera including onion thrips(Thrips tabaci Lindeman) and other foliar feeding thrips; and centipedesin the order Scutigeromorpha; and members of the Phylum or ClassNematoda including such important agricultural pests as root knotnematodes in the genus Meloidogyne, lesion nematodes in the genusPratylenchus, stubby root nematodes in the genus Trichodorus, cystnematodes such as Globodera pallida, Globodera rostochiensis,Paratrichodorus species and Longidorus species.

In a preferred embodiment of this invention, at least one phytophagousinvertebrate pest to be controlled is selected from the group consistingof G. pallida, G. rostochiensis, Trichodorus spp., Paratrichodorus spp.,Longidorus spp., free-living nematodes, Homopteran species (e.g.Aphids), Coleopteran species (e.g. wireworms and Colorado beetle) andLepidopteran species (e.g. Potato tuber moth). Especially preferred aremethods for controlling at least one pest selected from the groupconsisting of soil-inhabiting pests G. pallida, G. rostochiensis,Trichodorus spp., Paratrichodorus spp., Longidorus spp. Agriotes spp.Phthorimaea operculella and foliar-inhabiting pests Leptinotarsadecemlineata, Empoasca fabae and Eupterycyba jucunda.

The preferred crop to be protected from phytophagous invertebrate pestsis potato. The preferred phytophagous invertebrate pests to becontrolled in connection with potato are G. pallida and G.rostochiensis, with control of G. pallida being a problem for which thismethod is especially useful.

The methods of this invention provide control of diseases caused by abroad spectrum of fungal plant pathogens in the Basidiomycete,Ascomycete, Oomycete and Deuteromycete classes. They are effective incontrolling a broad spectrum of plant diseases, particularly foliarpathogens of ornamental, vegetable, field, cereal, and fruit crops.These pathogens include Plasmopara viticola, Phytophthora infestans,Peronospora tabacina, Pseudoperonospora cubensis, Pythiumaphanidermatum, Alternaria solani, Alternaria brassicae, Septorianodorum, Septoria tritici, Cercosporidium personatum, Cercosporaarachidicola, Pseudocercosporella herpotrichoides, Cercospora beticola,Botrytis cinerea, Monilinia fructicola, Pyricularia oryzae, Podosphaeraleucotricha, Venturia inaequalis, Erysiphe graminis, Uncinula necatur,Puccinia recondita, Puccinia graminis, Hemileia vastatrix, Pucciniastriiformis, Puccinia arachidis, Rhizoctonia solani, Sphaerothecafuliginea, Fusarium oxysporum, Verticillium dahliae, Pythiumaphanidermatum, Phytophthora megasperna, Sclerotinia sclerotiorum,Scierotium rolftsii, Erysiphepolygoni, Pyrenophora teres, Gaeumannomycesgraminis, Rynchosporium secalis, Fusarium roseum, Bremia lactucae andother generea and species closely related to these pathogens.

The preferred crop to be protected from diseases caused by fungal plantpathogens is potato. The preferred fungal plant diseases to becontrolled on potato are early blight and late blight caused byAlternaria solani and Phytophthora infestans respectively.

Serial Application Strategy

Crop protection agents typically have been applied to the crop (a) priorto or at the time of planting, or (b) during the growing season to thefoliar or growing parts of the plant.

Pre-plant applications have included for example, incorporation of thecrop protection agent into the soil or treatment of crop seeds. In someinstances, a crop protection agent may have been applied to the newlyemerged shoots of the crop. In these cases, the crop protection agenthas been typically applied as a single one-time dose that must protectthe plant for the entire growing season.

Alternatively, some crop protection agents have been applied during thegrowing season. These applications have been typically made by sprayingaqueous suspensions or solutions of crop protection agents onto thefoliar parts of the crop plant. In some instances it has been necessaryto make repeated applications of a crop protection agent to provideeffective season-long protection. However, such applications may nothave been completely efficacious because, for example, timelyapplications may not have been possible due to weather or other factors.Foliar applications also may have been ineffective because ofinsufficient coverage or distribution of the crop protection agent orpoor absorption and translocation of the crop protection agent to partsof the crop plant that were not treated. Application in the later partsof the growing season may also have been impractical because of the sizeand condition of the crop plant. Because of these factors, it has oftenbeen necessary to use greater amounts of crop protection agents toprovide effective protection.

As noted above, nematode control has been typically practiced by the useof soil fumigation and/or soil incorporation of granular nematocides.These methods have been typically limited to a single pre-plantapplication. Application of these methods is ordinarily not feasibleduring the growing season, because fumigation is often toxic to the cropplant and soil incorporation would often mechanically injure the plant.

Typically, the delivery of the active ingredient into the root locusresults in the disorientation of the nematode, preventing root invasion.However, the use of granular nematocides applied by incorporation intothe soil at planting may result in insufficient degree of persistence toprevent hatch of later emerging nematodes. This is illustrated in FIG.1, where Curve 11 represents a relative level of oxamyl in the soilafter application (in this Figure, oxamyl is applied by soilincorporation prior to planting of the potato crop). Line 12 representsa critical concentration of oxamyl in the soil sufficient to effectivelycontrol the nematode pests. Curve 11 thus shows a decline in oxamylconcentration over time (T) to below the critical concentration. Curve13 represents a relative population (hatch) of G. rostochiensis over 4-6weeks and Curve 14 represents a relative population (hatch) of G.pallida over 6-8 weeks. It will be evident that even when oxamyl isapplied at a level sufficient to control early-hatching nematodes (i.e.G. rostochiensis) the later-hatching nematodes (i.e., G. pallida) maynot be exposed to a sufficiently high concentration of the cropprotection agent to be effectively controlled.

By distribution of the same amount of active material in discrete dosesover the hatching period the degree of control is superior to thatachieved by a single application at planting. Furthermore, thecommencement of treatment can be delayed until roots become active andbegin to release the hatching agents. This scheme is illustrated in FIG.2, where Curves 11 a, 11 b, 11 c, and 11 d represent the relative levelsof oxamyl in the soil after a series of four applications (applied afterplanting of the potato crop) and Line 12 represents a criticalconcentration of oxamyl in the soil sufficient to effectively controlthe nematode pests. Curves 11 a, 11 b, 11 c and 11 d thus show thatalthough oxamyl concentration declines over time (T) for each singledose, concentrations above the critical concentration are renewed byusing multiple doses. Curve 13 and Curve 14 represent the relativepopulations of the nematodes G. rostochiensis and G. pallida,respectively, as described for FIG. 1. It is evident that the serialapplication of the crop protection agent provides a soil concentrationof oxamyl that is sufficient to maintain effective control of even thelater-hatching nematodes.

Typically, serial applications of conventional granular crop protectionagents are not feasible because the growing plant prevents incorporationof the granular nematicide into the soil. A subsequent foliarapplication of nematocides is typically not practical because thenematicide is not effectively translocated into the root zone, and thuswould require uneconomically high rates of application for effectivecontrol.

Introduction of the crop protection agents into the locus of the rootzone in accordance with this invention (e.g. by irrigation systems)provides an effective means of delivering serial doses of cropprotection agents. The method allows for easy control of the amount ofcrop protection agent applied and the timing of application. Inaddition, worker exposure to the crop protection agent can be minimizedby using a closed system transfer system.

Of note are embodiments of this invention wherein there are from 2 to180 applications in the series. Preferred are from 2 to 20 applications,and more preferred are from 3 to 15 applications in the series. Of noteare embodiments wherein the initial application in a series for agrowing season is made within seven days of planting; and embodimentswherein the initial application in a series for a growing season is madewithin seven days of the onset of the infestation period of a pest beingcontrolled. Also of note are embodiments wherein applications in theseries are spaced apart by at least 2 days (for example, from 4 to 14days apart). Preferrably, the series includes from 2 to 15 applicationsduring the infestation period of the pest being controlled.

Description of the Crop Protection Agents

Crop protection agents suitable for this method include one or moreinsecticides, fungicides, nematocides or acaricides. These cropprotection agents can also be mixed together with each other or withother agents such as bactericides, growth regulators, chemosterilants,semiochemicals, repellents, attractants, pheromones, feeding stimulants,fertilizers or other biologically active compounds to form amulti-component pesticide giving an even broader spectrum ofagricultural protection. Examples of such agricultural protectants are:insecticides such as abamectin, acephate, acetamiprid, avermectin,azadirachtin, azinphos-methyl, bifenthrin, binfenazate, buprofezin,carbofuran, chlorfenapyr, chlorfluazuron, chlorpyrifos,chlorpyrifos-methyl, chromafenozide, clothianidin, cyfluthrin,beta-cyfluthrin, cyhalothrin, lambda-cyhalothrin, cypermethrin,cyromazine, deltamethrin, diafenthiuron, diazinon, diflubenzuron,dimethoate, diofenolan, emamectin, endosulfan, esfenvalerate,fenothicarb, fenoxycarb, fenpropathrin, fenproximate, fenvalerate,fipronil, flucythrinate, tau-fluvalinate, flufenoxuron, fonophos,halofenozide, hexaflumuron, imidacloprid, indoxacarb, isofenphos,lufenuron, malathion, metaldehyde, methamidophos, methidathion,methomyl, methoprene, methoxychlor, monocrotophos, methoxyfenozide,nithiazin, novaluron, oxamyl, parathion, parathion-methyl, permethrin,phorate, phosalone, phosmet, phosphamidon, pirimicarb, profenofos,pymetrozine, pyriproxyfen, rotenone, spinosad, sulprofos, tebufenozide,teflubenzuron, tefluthrin, terbufos, tetrachlorvinphos, thiacloprid,thiamethoxam, thiodicarb, tralomethrin, trichlorfon and triflumuron;fungicides such as acibenzolar, azoxystrobin, benomyl, blasticidin-S,Bordeaux mixture (tribasic copper sulfate), bromuconazole, carpropamid(KTU 3616), captafol, captan, carbendazim, chloroneb, chlorothalonil,copper oxychloride, copper salts, cymoxanil, cyproconazole, cyprodinil(CGA219417),(S)-3,5-ichloro-N-(3-chloro-1-ethyl-1-methyl-2-oxopropyl)-4-methylbenzamide(RH 7281), diclocymet (S-2900), diclomezine, dicloran,difenoconazole,(S)-3,5-dihydro-5-methyl-2-(methylthio)-5-phenyl-3-(phenylamino)₄H-imidazol-4-one(RP 407213), dimethomorph, diniconazole, diniconazole-M, dodine,edifenphos, epoxiconazole (BAS 480F), famoxadone, fenamidone, fenarimol,fenbuconazole, fencaramid (SZX0722), fenpiclonil, fenpropidin,fenpropimorph, fentin acetate, fentin hydroxide, fluazinam, fludioxonil,flumetover (RPA 403397), fluquinconazole, flusilazole, flutolanil,flutriafol, folpet, fosetyl-aluminum, furalaxyl, furametapyr (S-82658),hexaconazole, ipconazole, iprobenfos, iprodione, isoprothiolane,kasugamycin, kresoxim-methyl, mancozeb, maneb, mefenoxam, mepronil,metalaxyl, metconazole, metominostrobin/fenominostrobin (SSF-126),myclobutanil, neo-asozin (ferric methanearsonate), oxadixyl,penconazole, pencycuron, probenazole, prochloraz, propamocarb,propiconazole, pyrifenox, pyraclostrobin, pyrimethanil, pyroquilon,quinoxyfen, spiroxamine, sulfur, tebuconazole, tetraconazole,thiabendazole, thifluzamide, thiophanate-methyl, thiram, triadimefon,triadimenol, tricyclazole, trifloxystrobin, triticonazole, validamycinand vinclozolin; nematocides such as aldicarb, oxamyl and fenamiphos;bactericides such as streptomycin; acaricides such as amitraz,chinomethionat, chlorobenzilate, cyhexatin, dicofol, dienochlor,etoxazole, fenazaquin, fenbutatin oxide, fenpropathrin, fenpyroximate,hexythiazox, propargite, pyridaben and tebufenpyrad; and biologicalagents such as Bacillus thuringiensis including ssp. aizawai andkurstaki, Bacillus thuringiensis delta endotoxin, baculovirus, andentomopathogenic bacteria, virus and fungi.

Preferred invertebrate pest control agents include oxamyl, aldicarb,ethoprophos, fenamiphos and fosthiesate, with oxamyl especiallypreferred.

Preferred fungicidal plant protection agents include cymoxanil,famoxadone, fenamidone, oxadixyl and metalaxyl.

Active ingredients used in accordance with the methods of this inventionmay optionally be used as a formulation or composition with anagriculturally suitable carrier comprising at least one of a liquiddiluent or a surfactant that is further diluted with water. Theformulation or composition ingredients are selected to be consistentwith the physical properties of the active ingredient, mode ofapplication and environmental factors such as soil type, moisture andtemperature. Useful formulations include liquids such as solutions(including emulsifiable concentrates), suspensions, emulsions (includingmicroemulsions and/or suspoemulsions) and the like. Useful formulationsfurther include solids such as dusts, powders, granules, pellets,tablets, films, and the like that are water-soluble.

The formulations will typically contain effective amounts of activeingredient, diluent and surfactant within the following approximateranges that add up to 100 percent by weight. Weight Percent ActiveIngredient Diluent Surfactant Water-soluble Granules, Tablets and 5-90 0-94 1-15 Powders. Suspensions, Emulsions, Solutions 5-50 40-95 0-15(including Emulsifiable Concentrates)

Typical liquid diluents are described in Marsden, Solvents Guide, 2ndEd., Interscience, New York, 1950. McCutcheon 's Detergents andEmulsifiers Annual, Allured Publ. Corp., Ridgewood, N. J., as well asSisely and Wood, Encyclopedia of Surface Active Agents, Chemical Publ.Co., Inc., New York, 1964, list surfactants and recommended uses. Allformulations can contain minor amounts of additives to reduce foam,caking, corrosion, microbiological growth and the like, or thickeners toincrease viscosity.

Surfactants include, for example, polyethoxylated alcohols,polyethoxylated alkylphenols, polyethoxylated sorbitan fatty acidesters, dialkyl sulfosuccinates, alkyl sulfates, alkylbenzenesulfonates, organosilicones, N,N-dialkyltaurates, lignin sulfonates,naphthalene sulfonate formaldehyde condensates, polycarboxylates, andpolyoxy-ethylene/polyoxypropylene block copolymers. Liquid diluentsinclude, for example, water, N,N-dimethylformamide, dimethyl sulfoxide,N-alkylpyrrolidone, ethylene glycol, polypropylene glycol, propylenecarbonate, dibasic esters, paraffins, alkylbenzenes, alkylnaphthalenes,oils of olive, castor, linseed, tung, sesame, corn, peanut, cotton-seed,soybean, rape-seed and coconut, fatty acid esters, ketones such ascyclohexanone, 2-heptanone, isophorone and4-hydroxy-4-methyl-2-pentanone, and alcohols such as methanol,cyclohexanol, decanol, benzyl and tetrahydrofurfuryl alcohol.

Solutions, including emulsifiable concentrates, can be prepared bysimply mixing the ingredients. Granules and pellets can be prepared byspraying the active material upon preformed granular carriers or byagglomeration techniques. See Browning, “Agglomeration”, ChemicalEngineering, Dec. 4, 1967, pp 147-8, Perry's Chemical Engineer'sHandbook, 4th Ed., McGraw-Hill, New York, 1963, pages 8-57 andfollowing, and PCT Publication WO 91/13546. Pellets can be prepared asdescribed in U.S. Pat. No. 4,172,714. Water-soluble granules can beprepared as taught in U.S. Pat. No. 4,144,050, U.S. Pat. No. 3,920,442and DE 3,246,493. Tablets can be prepared as taught in U.S. Pat. No.5,180,587, U.S. Pat. No. 5,232,701 and U.S. Pat. No. 5,208,030. Filmscan be prepared as taught in GB 2,095,558 and U.S. Pat. No. 3,299,566.

For further information regarding the art of formulation, see T. S.Woods, “The Formulator's Toolbox—Product Forms for Modern Agriculture”in Pesticide Chemistry and Bioscience, The Food-Environment Challenge,T. Brooks and T. R. Roberts, Eds., Proceedings of the 9th InternationalCongress on Pesticide Chemistry, The Royal Society of Chemistry,Cambridge, 1999, pp. 120-133. See also U.S. Pat. No. 3,235,361, Col. 6,line 16 through Col. 7, line 19 and Examples 10-41; U.S. Pat. No.3,309,192, Col. 5, line 43 through Col. 7, line 62 and Examples 8, 12,15, 39, 41, 52, 53, 58, 132, 138-140, 162-164, 166, 167 and 169-182;U.S. Pat. No. 2,891,855, Col. 3, line 66 through Col. 5, line 17 andExamples 1-4; Klingman, Weed Control as a Science, John Wiley and Sons,Inc., New York, 1961, pp 81-96; and Hance et al., Weed Control Handbook,8th Ed., Blackwell Scientific Publications, Oxford, 1989.

A typical composition for the principle embodiment is a liquidformulation comprising a variable percentage of oxamyl activeingredient. The solubility of oxamyl in water and subsequent dispersionin soil makes it an ideal candidate for utilization in this method. Aparticularly useful composition for this method is a liquid concentrateformulation comprising 10% oxamyl as active ingredient, as describedbelow. This liquid concentrate is further diluted with water anddelivered to the crop field by an irrigation system (e.g. the systemdescribed below). Composition A Concentration Ingredients CAS # (% wt)Purpose Oxamyl, pure 23135-22-0 10.00 Active Ingredient Oxamyl technicalvarious 1.00 Technical Impurities impurities Citric acid 77-92-9 1.00Buffer FD&C Yellow #5 1934-21-0 0.03 Dye FD&C Blue #1 3844-45-9 0.02 DyeSucrose Octaacetate 126-14-7 0.10 Embittering Agent (SOA) Water7732-18-5 87.85 Diluent

This product is prepared by diluting a 60% oxamyl-in-water mixture(prepared during the manufacture of “oxamyl technical product”) by waterand adding citric acid and dyes (and also SOA, as needed).

Using an Irrigation System

It will be evident that the size of the perforations and/or pores in theconduit used for applying the crop protection agent should be sized sothat the crop protection agent can effectively emanate from the conduit.The ability to deliver the required serial dose may be practicallyeffected by utilizing an irrigation system already in use by somegrowers to supply water to developing crops. Preferrably, perforated orporous tubing is positioned above the planted tuber at planting, withpositioning below the surface of the soil being especially desirable.Trickle tape (e.g. T-tape) is particularly effective tubing for deliveryof the active ingredient to the locus of the root of the crop plant. Thetape is designed to emit water and the outlets are designed so that theprobability of blockages is low. Conventional equipment may be used toplace the tape in the ridge as the crop is planted. The trickle tape maythen be connected to the main supply pipe(s) fed by a pump (filters maybe used as appropriate). A transfer system for introduction of theactive ingredient into the water flowing to the crop may be positionedeither upstream or downstream of the pump. The introduction may becarried out, for example, via a Venturi system (see below). FIG. 3illustrates the basic elements of a typical operating system (20)comprising a water source (22), pump supply pipe (24), a pump unit (26),field supply pipes (28) and perforated or porous conduits (30). Trickletape, equipment for its placement in the ridge, and other irrigationsystem components are available from various irrigation supply houses(e.g. Field Irrigation, Asparagus Farm, Court Lodge Road, Appledore,Kent, TN26 2DH, UK).

Description of A Closed System Transfer System

The method of this invention may employ a closed system transfer systemfor mixing a liquid concentrate (e.g., a suspension, emulsion orsolution) of a crop protection agent with water prior to delivery to thelocus to be treated. In a preferred embodiment the means ofincorporating the crop protection agent comprises a venturi injectionapparatus. In another preferred embodiment, the means of incorporatingthe crop protection agent comprises a computer-controlled meteringsystem.

A suitable closed system transfer injection apparatus is illustrated inFIG. 4. The apparatus (40) comprises a product container (42) connectedto an injection tank (44) via a transfer tube (46). The transfer tube isdesigned to provide flow of active ingredient from the product container(42) to the injection tank (44) without release of the active ingredientto the outside environment. A transfer valve (not shown) may be includedwithin the transfer tube (46) to control the flow of active ingredient.The apparatus (40) further comprises a discharge tube (48) suitable forconnection to a device (e.g. the venturi apparatus described below) formixing the active ingredient with irrigation water prior to delivery tothe field irrigation system. A flow meter (50) and a ball valve (52) arepositioned along the length of the tube (48) to control flow of theactive ingredient from the injection tank (44). Quick connect (54) andquick connect (56) are provided as hose connections to allow for rinsingthe product container (42) and the injection tank (44) respectively withwater. The quick connect (56) for rinsing the injection tank (44) isconnected to a tank rinse nozzle (58) centrally positioned within theinjection tank (44) to facilitate rinsing of the entire interior of thetank. Water introduced through the quick connects, especially quickconnect (54) can be used to reduce the concentration of activeingredient relative to that in the product container (42). The sidewall(59) of the injection tank (44) may be made of transparent material toallow for observation of its contents (including the tank rinse nozzle(58)).

FIG. 5 illustrates a venturi apparatus (60) that may be used inconnection with the method of this invention (e.g., with the closedsystem injection apparatus (40) described above). In the venturiapparatus (60) shown, a pipe (62) for delivering water from a watersource to a crop field for irrigation is connected to a venturi pipe(64). A Venturi device (66) is positioned along the Venturi pipe (64)and is connected to an injection tube (68) positioned at the throat ofthe Venturi (66). The injection tube (68) is designed for connection toa source of active ingredient (e.g. the discharge tube (48) of theapparatus illustrated in FIG. 4) to allow for injection of activeingredient into the water passing through the pipe (64). Ball valve (70)and ball valve (72) are positioned along the Venturi pipe (64) at itsupstream and downstream connections to the pipe (62), respectively, anda flow control valve (74) is positioned along pipe (62) between itsupstream and downstream connections to the Venturi pipe (64). The valves(70), (72) and (74) can be used to control both the overall flow ofwater through the pipes (62) and (64) and the relative flow of waterbetween pipe (62) and pipe (64).

The advantages of this particular system include the low potential forboth operator exposure and accidental contamination of the water source.

BIOLOGICAL EXAMPLES OF THE INVENTION TEST A Control of G. pallida byoxamyl

G. pallida is the more pernicious pest of potatoes. Studies have beenconducted with Composition A comprising oxamyl as described above.

The test units consisted of large diameter pots each containing onepotato plant, planted in soil amended with eggs of G. pallida at either24 cysts per pot (estimated to be about 10 eggs/g of soil) or 120 cystsper pot (estimated to be about 50 eggs/g of soil). These pest burdensrepresent a level of infestation that would require treatment in orderto prevent crop damage and potential multiplication of the pest (10eggs/g of soil) and substantial yield loss (50 eggs/g of soil).

Composition A was introduced into the test units diluted in a constantvolume of water. Applications of total active ingredient (ai) of oxamylat rates of 3.5 kg ai, 4.5 kg ai or 5.5 kg ai equivalent per hectarewere made either as a single dose (full dose applied at the start of theexperiment (3.5 kg/ha ai, 4.5 kg/ha ai or 5.5 kg/ha ai) or a series ofaliqots at intervals of either 4-day, 7-day or 14-day intervals. Theserial aliquot applications were made as follows to the infested soils:one fourteenth of the dose applied at the start of the experiment andrepeated every 4 days (fourteen treatments) for each of the dosesdefined above; one eighth of the dose applied at the start of theexperiment and repeated every 7 days (eight treatments) for each of thedoses defined above; one fourth of the dose applied at the start of theexperiment and repeated every 14 days (four treatments) for each of thedoses defined above. The dose at each application was applied in thesame volume of water and in equal incremental quantities. Controlexperiments were left untreated. The number of cysts attached to theroots per gram of root mass (washed free of soil) was determined at 70days (10 weeks) after commencement of the trial. This measurementindicates that the degree of control and the duration of theapplications adequately covered the potentially extended hatching periodof G. pallida. The tests were replicated four times and the results arereported as the average of the four replicates.

The results for the initial infestation of 10 eggs per gram of soil(from 24 cysts per pot) are shown in FIG. 6, and the results for aninitial infestation of 50 eggs per gram of soil (from 120 cysts per pot)are shown in FIG. 7. FIGS. 6 and 7 each show, for the respective initialinfestation, the number of cysts per gram of root mass after 70 days forvarious treatment alternatives. The runs illustrated in FIG. 6 and FIG.7 include an untreated control (run A), a single treatment of 3.5 kg/haat the beginning of the 70 days (at planting) (run B), a treatmenttotaling 3.5 kg/ha allocated over a series of 14 applications spaced in4 day intervals (run B4), a treatment totaling 3.5 kg/ha allocated overa series of 8 applications spaced in 7 day intervals (run B7), atreatment totaling 3.5 kg/ha allocated over a series of 4 applicationsspaced in 14 day intervals (run B14), a single treatment of 4.5 kg/ha atthe beginning of the 70 days (at planting) (run C), a treatment totaling4.5 kg/ha allocated over a series of 14 applications spaced in 4 dayintervals (run C4), a treatment totaling 4.5 kg/ha allocated over aseries of 8 applications spaced in 7 day intervals (run C7), a treatmenttotaling 4.5 kg/ha allocated over a series of 4 applications spaced in14 day intervals (run C14), a single treatment of 5.5 kg/ha at thebeginning of the 70 days (at planting) (run D), a treatment totaling 5.5kg/ha allocated over a series of 14 applications spaced in 4 dayintervals (run D4), a treatment totaling 5.5 kg/ha allocated over aseries of 8 applications spaced in 7 day intervals (run D7), and atreatment totaling 5.5 kg/ha allocated over a series of 4 applicationsspaced in 14 day intervals (run D14).

The data indicate that superior control of cyst production by G. pallidacan be achieved by distributing serial small of doses of activeingredient on a temporal basis at either 4-day, 7-day or 14-dayintervals, over the hatching period, compared to the equivalent doseapplied at planting in one application irrespective of the initial pestburden.

1. A method of protecting crop plants by controlling phytophagousinvertebrate pests, plant diseases caused by fungal pests, or both,comprising: applying a series of doses of an aqueous mixture containingan effective amount of a crop protection agent to the locus of the rootsof the crop plants by means of perforated or porous conduit on or nearthe surface of the soil; at least one dose of said series being appliedin the period from one week prior to planting to two days prior toharvest; and at least two doses of said series being applied at leasttwo days apart during the growing season of the crop or the infestationperiod of a pest being controlled.
 2. The method of claim 1 wherein asoil-inhabiting invertebrate pest is controlled by applying an effectiveamount of the aqueous mixture containing a crop protection agent to thesoil at the locus of the roots of the crop plant.
 3. The method of claim2 wherein potatoes are protected from at least one pest selected fromthe group consisting of G. pallida, G. rostochiensis, Trichodorus spp.,Paratrichodorus spp., Longidorus spp. Agriotes spp. and Phthorimaeaoperculella.
 4. The method of claim 3 wherein potatoes are protectedfrom G. pallida.
 5. The method of claim 4 wherein the crop protectionagent is selected from the group consisting of oxamyl, aldicarb,ethoprophos, fenamiphos and fosthiesate.
 6. The method of claim 5wherein the crop protection agent is oxamyl.
 7. The method of claim 6wherein the crop protection agent is applied in a series of from 4 to 14applications.
 8. The method of claim 7 wherein the initial applicationin the series for a growing season is made within seven days ofplanting.
 9. The method of claim 1 wherein a fungal disease caused by asoil-inhabiting fungal pathogen is controlled by applying an effectiveamount of the aqueous mixture containing a crop protection agent to thesoil at the locus of the roots of the crop plant.
 10. The method ofclaim 1 wherein a foliar-inhabiting invertebrate pest is controlled byapplying to the soil at the locus of the roots of a crop plant aneffective amount of the aqueous mixture containing a crop protectionagent which is then taken up by the plant from the soil.
 11. The methodof claim 10 wherein potatoes are protected from at least one pestselected from the group consisting of Leptinotarsa decemlineata,Empoasca fabae and Eupterycyba jucunda.
 12. The method of claim 1wherein a fungal disease caused by a foliar-inhabiting fungal pathogenis controlled by applying to the soil at the locus of the roots of acrop plant an effective amount of the aqueous mixture containing a cropprotection agent which is then taken up by the plant from the soil. 13.The method of claim 12 wherein potatoes are protected from at least onefungal disease caused by a fungal pathogen selected from the groupconsisting of Phytophthora infestans and Alternaria solani.
 14. Themethod of claim 1 wherein the initial application in the series for agrowing season is made within seven days of the onset of the infestationperiod of a pest being controlled.